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Mobile battery fire breaks out on Tokyo’s main commuter line

Casey Baseel Jul 21, 2025
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Battery began to burn after less than a minute of use, owner says.

Tokyo’s Yamanote Line, which loops around the center of the city, is Japan’s most infamously crowded commuter train line, and a stressful should-to-shoulder stint on it is part of the daily trip to/from the office for many Tokyoites. The atmosphere tends to be more relaxed outside of rush hour, and on weekends in particular, but last Sunday was a startling exception.

At around 4:10 in the afternoon on July 20, passengers on a train traveling on the Yamanote’s “inner”/counterclockwise route between Shin Okubo and Shinjuku Stations noticed white smoke rising from the bag of a passenger. The bag’s owner, a woman in her 30s, reached inside, where she had her smartphone connected to a mobile battery for charging. She disconnected her phone, but by this time the battery itself was on fire.

A passenger hit the emergency stop button while another quick-thinking individual grabbed the train car’s onboard fire extinguisher and began spraying the bag. The woman sustained burns to her fingers and a total of four other passengers suffered injuries such as bruises and sprained ankles in the rush to evacuate the train, but all are expected to make quick and complete recoveries.

▼ A report showing images of the charred remains of the bag the battery was inside.

In speaking with investigators from the Tokyo Metropolitan Police, the woman said that she’d only had her phone plugged into the battery for “about 30 seconds” before it began to burn.

While there’s obviously never a good time for a fire to break out in an enclosed space, it’s fortuitous that the incident happened when it did, at a time when the train was comparatively uncrowded. During weekday morning and evening rush hours, it’s the norm for the Yamanote Line to be so crowded that it’s impossible to take a step in any direction unless the train is stopped at a station with its doors open and providing the bare minimum of wriggle room. The weekend mid-afternoon time also likely meant a lower ratio of sleepy, work-exhausted, on-their-way-home-from-drinking, or otherwise slow-reacting demographics that sometimes make up a sizeable amount of Yamanote ridership. Had the timing been different, the results of a fire inside a Yamanote train and subsequent hurried evacuation would have been far worse than a half-dozen or so minor injuries.

The incident comes less than two weeks after Japanese airlines instituted new rules for passengers regarding mobile batteries onboard airplanes. Currently JR East/East Japan Railway Company, which operates the Yamanote Line, has no formal regulations about the use or transport of mobile batteries on its trains, but Sunday’s fire may have the company considering adopting some, especially as the National Institute of Technology and Evaluation says that it has observed increased instances of mobile battery fires coinciding with higher temperatures during the summer months.

Source: NHK News Web, Nihon Keizai Shimbun via Hachima Kiko, YouTube/ANNNewsCH
Top image: Pakutaso
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